Attack power adds to your weapon damage which benefits the skill multiplier. If you have 150 attack and the skill is 2x the damage, it does 300. Attack power increases it to 175,which makes you do 350 damage.
Attack damages only adds damage after it is calculated. Say you do 300 damage, with attack damage it does 300+25 to the total of 325.
So as the attack power increases, you will output far more numbers than attack damage.
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